Cause of the Rapid Weakening of Typhoon Bebinca (0021) in the South China Sea

Abstract

ABSTRACT: The cause of the rapid weakening of Typhoon “Bebinca” was analyzed in this paper, by using the NCEP FNL (Final) Operational Global Analysis data on 1°×1° grids and the Tropical Cyclone (TC) Annual Report. The result shows that during the middle to late stage of its life cycle, the meteorological environments did not sustain “Bebinca” to maintain its intensity: the water vapor transport at low level decreased significantly; cold air intruded from north at low to middle level; both the divergence at high level and the convergence at low level reduced at the same time in the late stage. All these above factors restrained the development of “Bebinca”. In particular, the rapid reduction of sea surface temperature (SST) was the main factor that induced the rapid weakening of the Typhoon, which occurred about 6 hour ahead of its weakening. Compared to the 500-850 hPa vertical wind shear, which shows a relatively high correlation with the weakening, the impact of the 200-850 hPa vertical wind shear on the intensity change was not significant. Therefore, the Typhoons in the South China Sea would possibly weaken and disappear rapidly in fall and winter. So we have to pay more attention to the time effectiveness of the forecasting and correct the results in time. Keywords: typhoon, rapid weakening, diagnosis